Keep all records of the Note and Mortgage you sign at the time of closing. Never throw these away.
Keep all records sent to you (or that you send to the bank) whether postal mail, email, fax.
Document all phone conversations that you have with bank representatives. This includes their name, employee ID if they have one, the day and time of call and detailed information about the phone conversation. Some states allow you to record people without telling them whereas other do not which makes it illegal. You should speak with an attorney to find out if you live in one of these states. Otherwise, the bank records all of their calls you can simply tell them that you are recording the phone conversation also and if they agree you may continue.
Never send copies of you Deed, Note and/or Mortgage to the bank if they request it. If they are requesting it it is most likely because they have lost it. This is good news for you because they won’t get far in court without it as long as you contest it.